Myself.
I am working on a '55 Chevy 210, building the car for drag racing. I am slowly getting rid of bits and pieces that I do not want anymore in an attempt to keep my garage space somewhat under control. (That might be me just dreaming though.) So on the a-arms, I had tried to sell them through various channels with no luck and while I could purchase a new set of mounting arms, I decided that if I could not get rid of them, I would just remove the mounting arms and junk the rest of it. Instead of trying to beat out 65 year old bushings, I broke out my plasma cutter. I got things hooked up, found an old piece of wood panel to do the cutting on and proceeded to try and cut the ends off of the a-arms. I have only used this plasma cutter twice before and it worked just fine. Today, no such luck. I could get an arc, but it would just stick to the work and I had to keep breaking it loose. I tried several times, but all I did was ruin the tip. So I replaced the tip with a spare. I then start checking voltages as this is a 220v cutter. Everything looked good. Then I pulled the plasma cutter out of the welding cart and started messing with the setup dials, trying different amperage, and varying the rate of cut - nothing worked.
I was sitting there trying to figure out what could be wrong with a brand new piece of equipment when I noticed that I had not connected the air line to the cutter!
Sometimes, I am my own worst enemy.